This invention relates to a apparatus for damping a pulsation of a fluid conveyed through a conveying device. The apparatus is particularly directed to a device in which fluid flows through a first tubular element into a cavity formed by a flexible element and emerges from the cavity by way of a second tubular element. The first and second tubular elements have a size and are arranged within the cavity of the flexible element such that the length of the individual tubular elements is smaller than the length of the cavity of the flexible element; however the sum of the lengths of the tubular elements is greater than the length of the cavity.
It is known to use conveying devices for conveying a fluid, for example a cooling or hydraulic unit. In this case, the fluid is conveyed from a suction side to a delivery side of the conveying device, at the same time with an increase in pressure, by means of a displacement unit. An appropriate conduit is connected to a delivery connection of the conveying device in order to transfer the conveyed fluid. The displacement unit normally possesses a plurality of displacement chambers, the conveyed part-volumes of which are combined to form a total volume flow of the conveying device. This causes the volume flow to pulsate. The temporary rise and fall in the pressure (pulsation) may be divided into individual pressure waves. Pulsations of this kind also occur when gaseous fluids are conveyed.
The pulsation of the fluid gives rise, on the one hand, to vibrations and, on the other hand, to disturbing noises.
In order to avoid these disadvantages, in the arrangements known hitherto the fluid has been led through tubular elements which are arranged in the fluid stream. It is also known to arrange the tubular elements in a cavity which is formed by a flexible element and through which the fluid flows. In this case, a first tubular element is used as an inflow and a second tubular element as an outflow. The two tubular elements are, in this case, arranged in such a way that their inflow and outflow orifices are located opposite one another and are arranged at a distance from one another. There is also a gap between the inflow and outflow orifices.
The cavity formed or enclosed by the flexible element is likewise filled with the fluid, and the fluid conveyed by the hydraulic conveying device flows from the inflow orifice of the first tubular element by way of the gap to the outflow orifice of the second tubular element. In this case, in the region of the gap, the fluid is damped as a result of interaction with the fluid located in the cavity. At the same time, on the one hand, the front of the pressure wave is widened due to turbulences which occur and, on the other hand, a cavity formed by the flexible element increases in size by virtue of the internal pressure which has risen. As soon as the internal pressure falls again, contraction of a flexible element occurs, this force likewise serving for conveying the fluid. In the arrangement known hitherto, however, pulsations continue to occur. Pulsation damping for this type of prior device is therefore insufficient.
The object on which the invention is based is to allow greater damping of the pulsation in a cost-effective way without any additional outlay in design terms.
To achieve this object, it is proposed to have a flexible element enclosing a cavity and to have two tubular elements positioned in the cavity of the flexible element. Under the present invention, the length of the individual tubular elements is less than the length of the cavity of the flexible element; however, the sum of the lengths of the tubular elements is greater than the length of the cavity. In this way, on the one hand, the distance from the inflow orifice to the outflow orifice is increased; on the other hand, the direction of flow of the fluid is reversed in the region between the inflow orifice and the outflow orifice. This results in advantageous pulsation damping.
The tubular elements consist, for example, of plastic or of metal, preferably of high-grade steel. Their composition may be adapted to the fluid to be conveyed and to the pulsations which occur. The flexible element is integrated via a sleeve, flange or the like into the circuit of the fluid to be conveyed. The said flexible element has a flexible wall which may consist, for example, of an elastomer.
Further preferred embodiments of the invention may be gathered from the remaining features which are mentioned in the subclaims.